Amorphophallus mayoi (Ittenb.) Eb.Fisch., B.Dumbo & L.Dumbo, 2022

Fischer, Eberhard, Dumbo, Bonny & Dumbo, Landry, 2022, A new species of Amorphophallus (Araceae) from Eastern D. R. Congo, and a new record of the genus from Rwanda, Plant Ecology and Evolution 155 (3), pp. 333-342 : 333

Amorphophallus mayoi (Ittenb.) Eb.Fisch., B.Dumbo & L.Dumbo comb. et stat. nov.

Figs 3 , 4 , 5

Amorphophallus calabaricus N.E.Br. subsp. mayoi Ittenb., Willdenowia 27(1-2): 159. 1997. ( Ittenbach and Lobin 1997: 159)

Type.

Uganda - U4 • Mengo Distr. , Kajansi Forest Reserve, 16 m on road to Entebbe; April 1938; Chandler 2433; holotype: K [K000609683, K000609684] .

Additional specimens studied.

D.R. CONGO - Forestier Central • à 8 km à l’ouest du Village Yakombe (route Yangambi-Gazi), forêt secondaire lianeuse à l’emplacement d’un ancient village appelé “Elongo”, endroit clairièré; 9 May 1940; Germain 340; BR [BR0000019942988] • Yangambi; Mar. 1949; Germain 4768; BR [BR0000019942995].

RWANDA - Lacs Edouard et Kivu • Western Province, Nyungwe National Park, Cyamudongo Forest, near Nyakabuye River; 1801 m; 1 Nov. 2019; B. Dumbo & M. Harbusch s.n.; KOBL.

Uganda - U2 • Bunyoro Distr., Budongo Forest; 28 June 1972; Synnott 1080; K • ibid.; Oct. 2005; Fischer & Killmann s.n.; KOBL • Mbale District, 10 km N of Busia, Oruchor Hill; 4 May 1951; Wood 257; K.

Kenya - K5 • N Kavirondo Distr., Kakamega Forest; 12 Apr. 197; O.J.Hansen 921; K, EA • ibid.; Oct. 2005; Fischer & Killmann s.n.; KOBL.

Habitat.

Closed canopy montane rainforest with dominating Newtonia buchananii (Baker) G.C.C.Gilbert & Boutique and Entandrophragma excelsum Sprague at 1801 m a.s.l.

Preliminary IUCN conservation assessment.

Amorphophallus mayoi is widespread and known from at seven localities, four of them under protection as Forest Reserve or National Park. It is assessed here as Vulnerable (VU B1a2a).

Taxonomic notes.

The leaves of a small Amorphophallus were discovered in 2016 during a botanical inventory of Cyamudongo Forest, a small isolated remnant forest of ca 300 ha that is protected as part of Nyungwe National Park. At the end of October 2019, a young inflorescence was discovered and it was subsequently identified as Amorphophallus calabaricus subsp. mayoi . This subspecies was originally described from Uganda, Kenya, and D.R. Congo, but had never been recorded for Rwanda. It is morphologically distinct from Amorphophallus calabaricus subsp. calabaricus that has a dark brown-purple upper spathe, a dark purple appendix that is at least 2 times as long as the spathe, and a longitudinal relation of carpellate and staminate area of 0.65 to 0.75. Amorphophallus calabaricus subsp. mayoi has an olive-green upper spathe, an olive-green to yellowish appendix that is not exceeding 1.5 of the length of spathe, and a relation of carpellate to staminate area of 0.7 to 1.3. While A. calabaricus subsp. calabaricus is restricted to coastal Nigeria and Cameroon in lowland rainforests of 50 to 500 m, A. calabaricus subsp. mayoi is found in Eastern D.R. Congo (Yangambi), Western Uganda (Budongo Forest, Entebbe), and Western Kenya (Kakamega Forest) in submontane to montane forests from 470 to 1801 m. These morphological, geographical, and ecological differences seem sufficient to consider Amorphophallus calabaricus subsp. mayoi as a species of its own. Amorphophallus mayoi is recorded here for the first time for Rwanda. The plant produces inflorescences at the end of October to November, and the leaves are shed at the end of November and last until March. A pronounced dormancy is observed from April to October. As the only hitherto published illustration is a reproduction of the herbarium specimen Wood 257 ( Ittenbach 2003), we provide pictures from the two main localities (Budongo Forest, Uganda and Kakamega Forest, Kenya) showing full developed inflorescences (Figs 3 , 4 ). The type at Kew consists of two sheets (sheet I, sheet II) under the number Chandler 2433 (K000609683, K000609684). There is a third specimen under this collector number Chandler 2433 (K000609685) from April 1939 and the original collector number is crossed out and Nr. 2433 is added. Thus, sheet III is not part of the type collection but was collected on the same place one year later.

Figures

Figure 3. Amorphophallus mayoi. A - E. Inflorescences. F. Leaf. Scale bars: 5 cm (A, C-E), 10 cm (B). Photographs taken by Eberhard Fischer at Kakamega Forest in February 2007 (A, C-D) and on 10 Apr. 2009 (F), and at Budongo Forest in February 2006 (B).

Figure 4. Amorphophallus mayoi. A - C. Inflorescences. D, G. Infructescences. E. Leaf. F. Detail of petiole. Scale bars: 5 cm (A-C), 1 cm (D, F-G), 10 cm (E). Photographs taken at Cyamudongo Forest on 1 Nov. 2019 by Bonny Dumbo (A-C) and on 31 Dec. 2017 by Eberhard Fischer (E), and at Budongo Forest on 11 Oct. 2005 by Eberhard Fischer (D, F-G).

Figure 5. A. Distribution map of Amorphophallus dumboi, A. margretae, and A. mayoi in D. R. Congo and Rwanda. B. Distribution map of A. mayoi.